"He developed a fear of failure and that’s why he became a teacher," Cranston told BuzzFeed. "It was a subliminal decision because you cannot criticize the profession of teacher. So if you develop a fear of failure, which is very common, people launch into something and then they get cold feet and say, 'Oh, I don’t know if I should do it.'
He’s hiding out in education. This is a brilliant chemist; if he decided to become a truck driver, people would say, 'What are you doing? You’re wasting your god-given talents, why would you do that?!' But no one would say that about becoming a teacher. So he has in a way cocooned himself in education. But that didn’t help to assuage his guilt or depression about missed opportunities in life.
I worked a lot on the subject of depression, because that’s where his kicking off point was. When we first meet him, he’s a man who loves his wife, loves his family, is responsible — but depressed.
[When Walter gets cancer] he doesn’t have room for depression. That’s the irony of these last two years of Walter White’s life, is that he’s so close to death is when he started to live, to be powerful, to be respected, to be able to intimidate another human being. These are very, very powerful things, especially for men. It makes a man’s chest go out. You see Walter White, whose physicality was hunched over under the weight of the world; when he becomes Heisenberg, he stands tall, with his hat."